EmbeddedUbuntu

Revision 30 as of 2006-06-22 14:08:43

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Summary

Embedded Linux is a fast growing option in the world of mobile devices, but the existing frameworks to embed Linux are either complex (e.g. use too many hacks to fake a native environment) or use proprietary code on the target side. This brings a lot of constraints to ease the porting of desktop applications to the handheld world and make a really Free embedded OS. Embedded Ubuntu is an initiative to build a community around the development of a highly flexible (albeit simple) framework to generate customised Ubuntu derivatives for target mobile devices.

Rationale

There are over 1 billion mobile phone users worldwide and over 2 billion connections. Such mobile devices, PDAs and new embedded devices such as Internet Tablets could be of more use to a wider population, mostly to those who cannot afford to pay high prices to have multimedia applications in their hands. Since the Ubuntu principle is to have Linux for human beings, to embed Ubuntu into such mobile devices is the fundamental basis of having people not only connected but humanly connected.

Use cases

  • Maria and her class mates of a primary school need to make up a report on how to protect the environment of dolphins, digitally recorded by them. They ask assistance from Jeff who selects a suitable subset of Ubuntu applications. He then generates an Embedded Ubuntu system image for the Internet Tablets they have and flashes it on the devices. The kids use Gstreamer, for example, and through WiFi connection they send their 5 minutes content to a 3G mobile phone of their teacher, which sends the content to other children in another city who have never seen a dolphin in their lives.

  • Miriam is a family practice physician who works on a remote village. She needs to send photos of her patients' lessons to an specialist in an advanced medical center to make the differential diagnostic. She receives an Embedded Ubuntu DVD with pre-selected suitable applications from a friend and installs it on her PDA/Internet Tablet. She accesses her office on the Internet through WiFi connection and her cell phone, sends the photos and discuss with the specialist.

Scope

EmbeddedUbuntu will initially cover only ARM-based platforms, preferably with a LCD display. This includes, for instance, ARM-based PDAs and Internet Tablets. Development is being done on the TI OMAP 5912 Starter Kit (see http://tree.celinuxforum.org/CelfPubWiki/OSK for more information about this device).

There are a number of OMAP (a popular embedded platform) devices already running Linux: http://www.muru.com/linux/omap/devices/. They should be easier to work with because there is kernel support for most of their hardware, so we will concentrate on supporting this class of devices first. There is also a good list of devices running linux on: http://www.handhelds.org/moin/moin.cgi/SupportedHandheldSummary

Implementation

  • Create an emulated environment of the target platform with no memory or storage restrictions. This allows us to use traditional tools like dpkg, debootstrap and apt-get to generate and update the target filesystem. (DONE)
    • Create a package that contains a statically linked version of QEMU ARM user emulator (qemu-arm-static)
    • Use dpkg-cross to install the ARM libc6 package on the host (usually not ARM-based).
    • Use the binfmt_misc kernel module to support running ARM binaries on non-ARM platforms, using QEMU as interpreter
  • Implement a cross-installation system (DONE)
    • Modify debootstrap to properly work for cross-bootstrapping, allowing us to create a minimal bootstrap system
  • Implement dpkg hooks that strip documentation (and other files not necessary for running applications).
  • Investigate a method to create system images to be flashed on the mobile device.

  • Investigate flashing methods for each platform (for OSK 5912: http://tree.celinuxforum.org/CelfPubWiki/FlashRecoveryUtility).

  • Select lightweight packages suitable (or easily adaptable) for use on embedded devices.
    • Select a set of applications to build a very simple reference system (for example, for demos); initially, GPE will be used as reference graphical environment.
    • Package the rest of GPE modules not yet on universe.
    • Create an archive with a pool of ARM packages ready to be installed on the embedded system. Not all applications currently available on Ubuntu are suitable for embedded hardware, so they should be ommited on this archive.
  • Compile Linux kernel and bootloader to specific platforms (tested and working for OSK 5912 platform).
  • Distribution mechanism: create installation CD with tools needed to flash the generated system images on mobile devices.

Data preservation and migration

The OS that was previously installed on the mobile device will be lost after flashing the customized Ubuntu. Support for backing up the previous OS can be added in future.

Outstanding issues

  • Some applications behave badly when running under QEMU. For instance, "update-gdkpixbuf-loaders" (run by some post-installation scripts) currently segfaults when running under QEMU. We should investigate why this happens and fix QEMU (or the application itself where aplicable). Some syscalls are not implemented in QEMU yet, but they do not seem to be critical for building and installing packages.
  • QEMU should be intensively tested for full system installation. For now it was tested for a minimal debootstrap installation. Basic client X libraries and applications also installed without problems. Package building (using debuild) worked fine too.

BoF agenda and discussion

  • FabioDiNitto suggested either building packages natively or using pre-built cross-toolchains to build the ARM archive. Packaging cross-toolchains for each host-target combination would be unpractical.

  • LaMontJones explained a lot about how Build Daemons work and how a new archive pool is created. He also suggested using breezy as a base and initially building main (maybe not whole main?) and those packages from universe we might need.

  • MattZimmerman asked us to send the patches we have for existing packages, and submit the new packages for inclusion into universe, so we can have a working cross-development environmment for dapper.

  • [https://wiki.ubuntu.com/Silpol Silpol] suggested to consider [http://www.nokia.com/770 Nokia 770] as potential platform for development - start with taking software from [http://maemo.org/ Maemo.org], strip what seems to be not necessary (try to retain core SW as much as possible), and build on top of it. Comments/feedback requested.

Similar projects

* The Familiar Distribution is a distribution for Handhelds. http://familiar.handhelds.org

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